Democrats may be only too happy to let him follow through on his threat since it will now be easy for them to blame the president for any government interruption, which would probably aggravate many Americans.

Rather than cowing Democrats, Mr. Trump’s tough talk is more likely to embolden the opposition in ongoing negotiations, particularly since he has now twice suggested he was willing to shutter government agencies if he didn’t get his way.

It also puts more pressure on Republicans to find the votes internally to pass spending bills and an increase in the federal debt limit — two things hard-right conservatives in the House and Senate have refused to support in the past. That Republican resistance provides Democrats leverage — Republicans can either grant concessions such as no wall money or produce all the votes for the spending bills and debt limit increase themselves.